BQ25050 Datasheet, PDF (16/28 Pages) Texas Instruments – 1A, Single-Input, Single Cell Li-Ion Battery Charger with 50-mA LDO, External Power Path

bq25050
SLUSA33 – MARCH 2010
www.ti.com
Under-Voltage Lockout (UVLO)
The bq25050 remains in power down mode when the input voltage is below the under-voltage lockout threshold
(VUVLO). During this mode, the control input (CTRL) is ignored. The LDO, the charge FET connected between
IN and OUT are off and the status output (CHG) is high impedance. Once the input voltage rises above V_UVLO,
the internal circuitry is turned on and the normal operating procedures are followed.
Input DPM Mode (VIN-DPM)
The input current into the bq25050 includes all load currents, i.e. the system load, LDO load, and battery charge
current. The total input current is regulated by the input current limit of the bq25050. The bq25050 utilizes the
V_IN-DPM mode for operation from current-limited input sources. V_IN-DPM is enabled at startup and active until
disabled by the CTRL interface. See the Single Input Interface (CTRL) section for more details.
When _VIN-DPM is enabled, the input voltage is monitored. If V_IN falls to V_IN-DPM, the input current limit is reduced
to prevent the input voltage from falling further. This prevents the bq25050 from crashing poorly designed or
incorrectly configured USB sources. Figure 24 shows the V_IN-DPM behavior to a current limited source. In this
figure the input source has a 200mA current limit and the device has started up with the 285mA current limit.
V_IMON
V_IN
I_LIM
Input voltage falls due to
adapter current limit
Input current limit is
reduced to prevent
crashing the input
supply
500 mV/div
2 V/div
200 mA/div
1 ms/div
Figure 24. bq25050 V_IN-DPM
External NTC Monitoring (TS)
The bq25050 provides a TS input for monitoring an external 47kΩ NTC thermistor. There are 2 temperature
thresholds that are monitored; the cold battery threshold (T_COLD) and the hot battery threshold (T_HOT). The TS
input is monitored at all times and disables charge if the temperature of the NTC falls outside of the operating
range. The operating range by default is 0°C to 45°C. An extended range of 0°C to 60°C is selectable using the
CTRL input. V_TS is also used to monitor the battery temperature. The temperature range is based on the NTC
thermistor #NCP15WB473F.
The TS function remains on during battery discharge to enable the host to monitor the battery temperature. The
VTS reflects the battery temperature the same as when the battery is charged. The bq25050 does not monitor
this voltage, only the current source is active. Table 1 shows important temperatures and the corresponding
voltage. This table can be used by the host to determine proper operation limits. The TS function is disabled if
the CHG voltage falls below logic low while in battery discharge mode.
16
Submit Documentation Feedback
Product Folder Link(s): bq25050
Copyright © 2010, Texas Instruments Incorporated